SecondLanguage lets you use Gettext files in .NET without a lot of hassle. It can read and write both .mo and .po, and fully supports message contexts and plural forms. A C-style printf formatter is included, so you don't have to use .NET-specific translations.

ENet for C# wraps the C-language ENet networking library. For games and other realtime applications, if you use TCP, old data can hold up newer data, even if it is no longer relevant (old positions, etc.). Your players will perceive any lost packet as a "lag burst". ENet supports multiple in-order streams of data, and allows you to decide on reliability on a per-packet basis. The library is useful for both client-server and peer-to-peer architectures.

CryptSharp provides a number of password crypt algorithms: BCrypt, MD5 (and Apache's htpasswd variant), PHPass (WordPress, phpBB, Drupal), SHA256, SHA512, and Traditional and Extended DES. It also includes Blowfish, SCrypt, and PBKDF2 for any HMAC (.NET's built-in PBKDF2 implementation supports only SHA-1). If you are looking to store passwords, odds are CryptSharp will have the algorithm you want.

NetIRC2 is an easy-to-use .NET IRC client library. It supports all major features relevant to making a chat client or bot. It has full support for synchronization contexts. You can use it from a Windows Forms or WPF GUI thread and chat events will be automatically dispatched, allowing you to completely ignore multithreading. It uses byte arrays internally, so mixed encodings can be handled. The IrcClient class can even be used as a component in the Forms Designer. Because it speeds up connect times with some IRC servers, an Ident server is included as well.

RemoteViewing is an embeddable .NET-native VNC client and server library.
It supports Raw, Hextile, Copyrect, and Zlib encodings, and includes a Windows Forms control to make embedding VNC in your program extremely easy.

Memview is a realtime visualization program which shows the memory state of another
running program as a graphical image.
Memory addresses correspond to pixels in the image,
and as memory is accessed, the display will
animate to show which parts of the address space are currently being referenced by the program.

Midao JDBC simplifies development with Java JDBC. It is flexible, customizable, and simple/intuitive to use, and provides a lot of functionality: transactions, working with metadata, type handling, profiling, input/output processing/converting, pooled datasource libraries support, cached/lazy query execution, named parameters, multiple vendor support out of the box, custom exception handling, and overrides. With a single jar, it supports both JDBC 3.0 (Java 5) and JDBC 4.0 (Java 6). Midao JDBC is well tested. Not only does it have around 700 unit and functional tests, but it's also tested with the latest drivers of Derby, MySQL (MariaDB), PostgreSQL, Microsoft SQL, and Oracle. Midao is a data-centric project. Its goal is to shield Java developer from nuances of vendor implementation and standard boilerplate code. Midao JDBC is the first library released under it.

Capsule Tree is a general purpose, self-balancing tree data structure for large, ordered data sets. It is designed to provide the same characteristics as B-trees and B+trees, but built from the ground up for in-memory usage. In other words, there are no provisions for “slow” I/O cases. The original motivation for this tree was a better backend for memory managers. However, the end result was a new sub-category of trees.